Impermanent biocompatible fastener

ABSTRACT

A biocompatible fastener particularly well-suited for use in fundoplication procedures. In a preferred embodiment, the fastener is designed to break within the span of approximately three to six months after implantation and comprises a male portion and a female portion. The male portion includes a first base member, the first base member being generally flat and oval. A pair of male members are mounted on the bottom surface of the first base member, each male member comprising a cylindrical post extending downwardly from the bottom surface of the first base member and a conical head disposed at the bottom end of the post. The female portion includes a second base member, the second base member being generally flat and oval. A pair of sleeves are mounted on the top surface of the second base member and extend upwardly therefrom. Each sleeve defines a bore adapted to receive a head from a corresponding male member and has an inner flange formed thereon. The flange extends radially into the bore and is engageable with the head once the head has been inserted therepast so as to inhibit withdrawal of the head from the bore. Except for an outer coating on each of the two heads, the fastener is made entirely of a non-bioabsorbable material or a bioabsorbable material having a relatively slow degradation rate. By contrast, the outer coating is made of a bioabsorbable material having a relatively fast degradation rate. The thickness of the outer coating is appropriately selected so that degradation of the outer coating permits each head to be withdrawn past its flange after a desired period of time.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 09/935,950, filed Aug. 23, 2001, now U.S. Pat. No. 6,692,507which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates generally to biocompatible fasteners andmore particularly to impermanent biocompatible fasteners.

Biocompatible fasteners have long been used to fasten together two ormore biological materials on or within a patient. Examples ofbiocompatible fasteners include sutures, staples, surgical glues, tissueclips and orthopedic fixation devices, such as bone plates, screws andthe like. For certain applications, such as where the biocompatiblefastener is implanted within a patient and is needed therewithin foronly a limited period of time, it is highly desirable that thebiocompatible fastener be impermanent or capable of degrading over timeso that an additional medical procedure not be required to remove thefastener from the patient. For this reason, many biocompatible fastenersnow in use are made entirely out of materials that, over time, becomechemically degraded within a patient and, ultimately, are fullymetabolized and excreted by the patient. (Other biocompatible fastenersare made out of materials that the body needs and are not excreted.)Such impermanent biocompatible fasteners are typically referred to inthe art as bioabsorbable fasteners and are made out of materialsincluding, but not limited to, homopolymers and copolymers of glycolide,lactide, ε-caprolactone and p-dioxanone, copolymers of glycolide andtrimethylene carbonate, as well as polyanhydrides and polyorthoesters.See Middleton et al., “Synthetic Biodegradable Polymers as MedicalDevices,” Medical Plastics and Biomaterials (March 1998), the disclosureof which is incorporated herein by reference.

Gastroesphageal reflux disease (GERD) is a disorder in which the loweresophageal sphincter, which is located in a distal portion of theesophagus adjacent to the junction between the esophagus and thestomach, allows contents of the stomach, including gastric acid andbile, to reverse flow into the distal portion of the esophagus duringdigestion. Complications associated with GERD include heartburn,pulmonary disorders, chest pain, esophageal ulcers, esophagitis,Barrett's esophagus, and esophageal carcinoma.

Although weight loss and/or prescription acid blockers are typicallypreferred treatment options for GERD, various surgical procedures havebeen devised to treat GERD where weight loss and/or prescription drugsare ineffective or impractical. In one surgical procedure, known asNissen fundoplication, a portion of the gastric fundus of the stomach iswrapped around the esophagus and is secured thereto using one or morebiocompatible fasteners, typically in the form of sutures, surgicalstaples or surgical two-part fasteners. The wrapped gastric fundusapplies pressure to the esophagus in such a way as to eliminate thereverse flow of stomach contents into the esophagus.

One of the more commonly used fundoplication procedures requiresabdominal or thoracic incisions through which the fundus wrapping andsecuring can be performed. Due to the highly invasive nature of suchsurgery, complications and morbidity occur in a significant percentageof cases. In addition, these procedures are time-consuming, often takinga number of hours to perform, and may leave disfiguring scars where theincisions were made.

More recently developed fundoplication procedures limit somewhat thenecessity of making large surgical incisions by utilizing laproscopicports or percutaneous endoscopic gastrostomy. Although these proceduresare less invasive than those involving large abdominal and thoracicincisions, they are still invasive and have certain risks associatedtherewith. For example, general anaesthesia, which entails well-knownrisks, is typically used during these procedures.

An even more recently developed fundoplication procedure is endoluminalfundoplication. In endoluminal fundoplication, a flexible endoscope ispassed first through a patient's mouth and then through the esophagus tolocate an attachment site at the gastroesophageal junction. A tissuegrasping device is then positioned at the distal end of the endoscopeand is attached to the located attachment site. Next, a tissuedisplacement device is positioned at the distal end of the endoscope andis used to displace the fundus of the stomach in such a way as to createan intussusception of the esophagus into the gastric lumen. A fastenerdelivery device is then used to secure the gastric fundus to theesophagus at a first location. The fastener delivery device is then usedto place additional fasteners at a plurality of additional desiredfastener locations, thus securing the gastric fundus entirely around theesophagus.

Examples of endoluminal fundoplication procedures are disclosed in U.S.Pat. No. 6,086,600, inventor Kortenbach, which issued Jul. 11, 2000, andin U.S. Pat. No. 6,113,609, inventor Adams, which issued Sep. 5, 2000,both of which are incorporated herein by reference.

In the aforementioned U.S. Pat. No. 6,113,609, there is disclosed afundoplication fastener that is made entirely out of a bioabsorbablematerial. One problem that has been noted by the present inventors isthat, whereas a fundoplication fastener need only be capable of securingthe gastric fundus to the esophagus for the approximately three- tosix-month period of time necessary for the gastric fundus and theesophagus to become fused to one another, a bioabsorbable fundoplicationfastener typically will remain in place for approximately two yearsbefore chemical degradation results in its structural decay.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a novelbiocompatible fastener.

Therefore, according to one aspect of the invention, there is provided abiocompatible fastener, said biocompatible fastener having a firstportion and a second portion, said first portion being made out of afirst bioabsorbable material, said first bioabsorbable material having afirst degradation rate, said second portion being made out of a materialselected from the group consisting of a non-bioabsorbable material and asecond bioabsorbable material, said second bioabsorbable material havinga second degradation rate, said second degradation rate being slowerthan said first degradation rate.

It is another object of the present invention to provide a novelimpermanent biocompatible fastener.

Therefore, according to another aspect of the invention, there isprovided a biocompatible fastener as described above wherein said firstportion is positioned within said biocompatible fastener so thatdegradation of said first portion results in fragmentation of thebiocompatible fastener.

It is still another object of the present invention to provide animpermanent biocompatible fastener that overcomes at least some of theshortcomings discussed above in connection with existing impermamentbiocompatible fasteners.

Therefore, according to still another aspect of the invention, there isprovided a biocompatible fastener that comprises, in a preferredembodiment, a male portion and a female portion. The male portionincludes a first base member, the first base member being generally flatand oval. A pair of male members are mounted on the bottom surface ofthe first base member, each male member comprising a cylindrical postextending downwardly from the bottom surface of the first base memberand a conical head disposed at the bottom end of the post. The femaleportion includes a second base member, the second base member beinggenerally flat and oval. A pair of sleeves are mounted on the topsurface of the second base member and extend upwardly therefrom. Eachsleeve defines a bore adapted to receive a head from a correspondingmale member and is provided with a pair of longitudinal slots that endowthe sleeve with some radial flexibility to facilitate insertion of ahead into the bore. In addition, each sleeve is provided with a sharptip at its top end to facilitate insertion of the sleeve throughbiological tissue. A substantially circumferential flange is formed onthe inside of each sleeve. The flange extends radially into the bore andis engageable with the head once the head has been inserted therepast soas to inhibit premature withdrawal of the head from the bore. Except foran outer coating on each of the two heads, the fastener is made entirelyof a non-bioabsorbable material. By contrast, the outer coating of theheads is made of a bioabsorbable material having a desired degradationrate. The thickness of the outer coating is appropriately selected sothat degradation of the outer coating after a desired period of timepermits each head to be withdrawn past its flange.

Because the heads of the aforementioned fastener are not made entirelyof a bioabsorbable material, but rather, are made of an inner core of anon-bioabsorbable material and an outer coating of a bioabsorbablematerial, the thickness of the bioabsorbable material is less than itwould otherwise be in a corresponding head made entirely out of thebioabsorbable material. Consequently, because of its reduced thickness,the bioabsorbable material becomes fully hydrated more rapidly and,therefore, degrades more quickly in the present fastener than in acorresponding fastener made entirely out of bioabsorbable material. As aresult, by selecting an appropriate bioabsorbable material and bydimensioning the fastener appropriately, the life-span of the fastenercan be tailored to the healing time for the fastened biologicalmaterial, e.g., three to six months for tissue subjected to afundoplication procedure.

As can readily be appreciated, instead of or in addition to making theheads out of an inner core of non-bioabsorbable material and an outercoating of bioabsorbable material, the flanges can be made out of aninner core of non-bioabsorbable material and an outer coating ofbioabsorbable material. A variety of other modifications to theaforementioned fasteners are also possible.

The above-described fasteners are amenable to being mass-produced byconventional molding techniques.

For purposes of the present specification and claims, it is to beunderstood that certain directional terms used herein, such as “top,”“bottom,” “upwardly,” “downwardly,” and the like, when used to describethe fastener of the present invention, are relative terms dependent uponthe fastener being situated in a particular orientation vis-á-vis theviewer at a particular point in time. As can readily be appreciated, ifthe orientation of the fastener is altered, such directional terms mayalso need to be altered correspondingly.

Additional objects, features, aspects and advantages of the presentinvention will be set forth, in part, in the description which followsand, in part, will be obvious from the description or may be learned bypractice of the invention. In the description, reference is made to theaccompanying drawings which form a part thereof and in which is shown byway of illustration specific embodiments for practicing the invention.These embodiments will be described in sufficient detail to enable thoseskilled in the art to practice the invention, and it is to be understoodthat other embodiments may be utilized and that structural changes maybe made without departing from the scope of the invention. The followingdetailed description is, therefore, not to be taken in a limiting sense,and the scope of the present invention is best defined by the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are hereby incorporated into andconstitute a part of this specification, illustrate preferredembodiments of the invention and, together with the description, serveto explain the principles of the invention. In the drawings wherein likereference numerals represent like parts:

FIG. 1 is a front view of a first embodiment of a biocompatible fastenerconstructed according to the teachings of the present invention, thebiocompatible fastener being shown, in an assembled state;

FIG. 2 is a perspective view of the biocompatible fastener of FIG. 1,the biocompatible fastener being shown in an unassembled state;

FIG. 3 is a fragmentary section view of the biocompatible fastener ofFIG. 1;

FIG. 4 is a fragmentary section view of a second embodiment of abiocompatible fastener constructed according to the teachings of thepresent invention, the biocompatible fastener being shown in anassembled state;

FIG. 5 is a fragmentary section view of a third embodiment of abiocompatible fastener constructed according to the teachings of thepresent invention, the biocompatible fastener being shown in anassembled state;

FIG. 6 is a front view of a fourth embodiment of a biocompatiblefastener constructed according to the teachings of the presentinvention, the biocompatible fastener being shown in an assembled state;

FIG. 7 is a fragmentary section view of the biocompatible fastener ofFIG. 6;

FIG. 8 is a perspective view of a fifth embodiment of a biocompatiblefastener constructed according to the teachings of the presentinvention, the biocompatible fastener being shown in an unassembledstate; and

FIGS. 9( a) through 9(d) are top views of alternative embodiments of thefemale portion of the biocompatible fastener of FIG. 8.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to FIGS. 1 through 3, there are shown various views of afirst embodiment of a biocompatible fastener constructed according tothe teachings of the present invention, said biocompatible fastenerbeing represented generally by reference numeral 11.

Fastener 11, which is particularly well-suited for, but is not limitedto, temporarily securing the gastric fundus to the esophagus as part ofa fundoplication procedure, is a two-piece, mating-type fastenercomprising a male portion 13 and a female portion 15.

Male portion 13, which may be made by molding, is a generally rigidstructure comprising a base 17. Base 17, which is generally flat andoval, has a top surface 17-1 and a bottom surface 17-2. A pair ofparallel male members 19-1 and 19-2 are disposed on opposite sides ofthe transverse centerline of base 17 and extend downwardly a shortdistance from bottom surface 17-2 of base 17. Male members 19-1 and 19-2are substantially identical to one another, each male member 19comprising a generally cylindrical post 21 terminating at its bottom endin a generally conical head 23.

Female portion 15, which may be made by molding, is a generally rigidstructure comprising a base 31. Base 31, which is generally flat andoval, has a top surface 31-1 and a bottom surface 31-2. A pair ofgenerally cylindrical, parallel sleeves 33-1 and 33-2 extend upwardly ashort distance from top surface 31-1 of base 31, sleeves 33-1 and 33-2being spaced apart appropriately for alignment with male members 19-1and 19-2, respectively. Sleeves 33-1 and 33-2 are substantially mirrorimages of one another taken along the transverse centerline of base 33,and it is to be understood that the description below of sleeve 33-1 iscorrespondingly applicable to sleeve 33-2.

Sleeve 33-1 terminates at its top end in a relatively sharp tip 35-1,tip 35-1 being so shaped to facilitate insertion of sleeve 33-1 throughbiological tissue or the like. Sleeve 33-1 is additionally shaped toinclude a longitudinally-extending bore 37-1 adapted to receive malemember 19-1. A pair of longitudinally-extending slots 39-1 and 39-2 thatare in fluid communication with bore 37-1 are provided in sleeve 33-1 toendow sleeve 33-1 with a certain degree of radial flexibility tofacilitate insertion of member 19-1 into bore 37-1. However, it shouldbe understood that, depending upon the applicable flexibilityrequirements of sleeve 33-1, one or both of slots 39-1 and 39-2 could bechanged in size or eliminated entirely and that one or more additionalslots could be provided in sleeve 33-1.

Sleeve 33-1 is further shaped to include a substantially circumferentialflange 41-1, flange 41-1 extending radially inwardly a short distanceinto bore 37-1. Flange 41-1 is appropriately sized so that, once head 23is inserted into bore 37-1 and past flange 41-1, head 23 cannot easilybe withdrawn from bore 37-1 back past flange 41-1, except under theconditions described below.

Referring now to FIG. 3, head 23 can be seen to comprise a core 23-1 anda coating 23-2. Core 23-1 is made out of a non-bioabsorbable material,and coating 23-2 is made out of a bioabsorbable material having adesired degradation rate. Said non-bioabsorbable material used to makecore 23-1 may be conventional in nature and may comprise one or morenon-bioabsorbable compounds. Said bioabsorbable material used to makecoating 23-2 may also be conventional in nature and may comprise one ormore bioabsorbable compounds.

The remainder of male portion 13 (and the entirety of female portion 15)is preferably made entirely out of the same non-bioabsorbable materialas core 23-1. Head 23 may be formed by insert molding coating 23-2 ontocore 23-1. Core 23-1 and coating 23-2 are appropriately sized relativeto flange 41-1 so that, when coating 23-2 becomes sufficiently degradedafter having been implanted within a patient for a particular period oftime, head 23 shrinks in size until head 23 is no longer retained inbore 37-1 by flange 41-1. (In other words, top surface 24 of head 23 isno longer engaged by flange 41-1.)

As can readily be appreciated, fastener 11 has a shorter life-span(i.e., will fragment sooner) than a corresponding fastener made entirelyout of a bioabsorbable material for the reason that the thickness of thebioabsorbable material in fastener 11 is considerably less than that ina corresponding “all-bioabsorbable” fastener. Consequently, because ofits reduced thickness, the bioabsorbable material of fastener 11 takesless time to become fully hydrated and, therefore, degrades more rapidlythan a corresponding “all-bioabsorbable” fastener.

It should be understood that one can alter the life-span of fastener 11by, among other things, modifying the type of bioabsorbable materialused in coating 23-2, modifying the thickness of coating 23-2, andmodifying the relative dimensions of core 23-1, coating 23-2 and flange41-1. It should also be understood that the non-bioabsorbable materialused to make all of fastener 11, except for coating 23-2, could bereplaced with one or more bioabsorbable materials having a slowerdegradation rate than the bioabsorbable material used to make coating23-2.

In addition, it should be understood that the number of sets of malemembers 19 and sleeves 33 in fastener 11 is illustrative only and that,in other embodiments, there could be as few as one male member 19 andone sleeve 33 or as many as three or more sets of male members 19 andsleeves 33.

Referring now to FIG. 4, there is shown a fragmentary section view of asecond embodiment of a biocompatible fastener constructed according tothe teachings of the present invention, the biocompatible fastener beingshown represented generally by reference numeral 61.

Fastener 61 is similar in many respects to fastener 11, fastener 61comprising a male portion 63 and a female portion 65, male portion 63being identical in overall size and shape to male portion 13 of fastener11, female portion 65 being identical in all respects to female portion15 of fastener 11.

The principal difference between fastener 61 and fastener 11 is thatmale portion 63 of fastener 61 is constructed to comprise, instead of apair of posts 21 each terminating at its bottom end in a generallyconical head 23, a pair of posts 67 each terminating at its bottom endin a generally conical head 69 (only one such post 67 and head 69 beingshown and described herein although it is to be understood that the twopost/head combinations are identical).

Post 67, which is cylindrical in shape, comprises a core 67-1 and acoating 67-2. Core 67-1 is made out of a non-bioabsorbable material, andcoating 67-2 is made out of a bioabsorbable material having a desireddegradation rate. Said non-bioabsorbable material used to make core 67-1may be conventional in nature and may comprise one or morenon-bioabsorbable compounds. Said bioabsorbable material used to makecoating 67-2 may also be conventional in nature and may comprise one ormore bioabsorbable compounds.

Head 69, which is conical in shape, comprises a core 69-1 and a coating69-2. Core 69-1 is made out of a non-bioabsorbable material, and coating69-2 is made out of a bioabsorbable material having a desireddegradation rate. Said non-bioabsorbable material used to make core 69-1may be conventional in nature and may comprise one or morenon-bioabsorbable compounds. Said bioabsorbable material used to makecoating 69-2 may also be conventional in nature and may comprise one ormore bioabsorbable compounds.

Coating 67-2 is appropriately sized relative to flange 41-1 so that,when coating 67-2 becomes sufficiently degraded after having beenimplanted within a patient for a particular period of time, head 69shrinks in size until head 69 is no longer retained in bore 37-1 byflange 41-1. As can be seen, as contrasted with head 23 of fastener 11,the entirety of the top surface 72 of head 69 of fastener 61 is made ofbioabsorbable material. This may be advantageous as it may preventtissue or other matter disposed on top surface 72 from being snagged bytop surface 72 and, in so doing, hindering the desired breaking apart offastener 61.

Cores 67-1 and 69-1 are preferably molded as a unitary structure withbase 70, with coatings 67-2 and 69-2 being simultaneously insert moldedthereover as a unitary coating.

It should be understood that one can alter the life-span of fastener 61by, among other things, modifying the type of bioabsorbable materialused in coatings 67-2 and 69-2, modifying the thicknesses of coatings67-2 and 69-2, and modifying the relative dimensions of core 69-1,coating 69-2 and flange 41-1. It should also be understood that thenon-bioabsorbable material used to make all of fastener 61, except forcoatings 67-2 and 69-2, could be replaced with one or more bioabsorbablematerials having a slower degradation rate than the bioabsorbablematerial used to make coatings 67-2 and 69-2.

Referring now to FIG. 5, there is shown a fragmentary section view of athird embodiment of a biocompatible fastener constructed according tothe teachings of the present invention, the biocompatible fastener beingshown represented generally by reference numeral 81.

Fastener 81 is similar in many respects to fastener 61, fastener 81comprising a male portion 83 and a female portion 85, male portion 83being identical in overall size and shape to male portion 63 of fastener61, female portion 85 being identical in all respects to female portion65 of fastener 11.

The principal difference between fastener 81 and fastener 61 is that thebottom portion of post 87 and the entirety of head 89 are made only ofbioabsorbable material whereas the remainder of post 87 comprises a core87-1 made out of a non-bioabsorbable material and a coating 87-2 madeout of a bioabsorbable material having a desired degradation rate. Ascan readily be appreciated, the relative lengths of core 87-1 and post87 can be modified as desired. It is to be noted that, because head 89is made entirely out of bioabsorbable material, as opposed to comprisinga coating of bioabsorbable material formed on a non-bioabsorbable core,head 89 may take comparatively longer to become fully hydrated.

Referring now to FIGS. 6 and 7, there are shown front and fragmentarysection views, respectively, of a fourth embodiment of a biocompatiblefastener constructed according to the teachings of the presentinvention, said biocompatible fastener being represented generally byreference numeral 101.

Fastener 101 is similar in many respects to fastener 11, the principaldifferences between the two fasteners being that fastener 101 comprisesa head 103 made entirely out of a non-bioabsorbable material and thatfastener 101 comprises a flange 105 comprising a core 105-1 and acoating 105-2, core 105-1 being made out of a non-bioabsorbable materialand coating 105-2 being made out of a bioabsorbable materials 105-2having a desired degradation rate. (It should be understood that thenon-bioabsorbable material used to make all of fastener 101, except forcoating 105-2, could be replaced with a bioabsorable material having aslower degradation rate than coating 105-2.)

As can readily be appreciated, fastener 101 could be modified byreplacing head 103 with head 23 of fastener 11, head 69 of fastener 61,head 89 of fastener 81 or the like. Alternatively, fastener 101 could bemodified by replacing flange 105 with a flange made entirely out of thebioabsorbable material of coating 105-2 and/or by replacing head 103with a head made entirely out of the bioabsorbable material of coating105-2.

Referring now to FIG. 8, there is shown a perspective view of a fifthembodiment of a biocompatible fastener constructed according to theteachings of the present invention, the biocompatible fastener beingrepresented generally by reference numeral 201.

Fastener 201 is similar in many respects to fastener 101, fastener 201comprising a male portion 203 and a female portion 205. Male portion 203is identical to the male portion of fastener 101.

Female portion 205 comprises a base 207, which in the present embodimentis generally rectangular in shape. Base 207 is made out of anon-bioabsorbable material and is shaped to include a pair of transversebores 209, each bore 209 being adapted to receive a head 103. A pair offlanges 211-1 and 211-2 made of a bioabsorbable material are disposedwithin each bore 209, flanges 211-1 and 211-2 being sized and shaped sothat, once head 103 is inserted therepast, head 103 cannot easily bewithdrawn from bore 209 back past flanges 211-1 and 211-2, unlessflanges 211-1 and 211-2 have degraded sufficiently. Flanges 211-1 and211-2 are preferably formed by insert-molding. Alternatively, in anotherembodiment, bore 209 and flanges 211-1 and 211-2 could be separatelyconstructed as an insert that is press-fit into a larger bore (notshown) previously formed in base 207.

As can readily be appreciated, the number of heads 103 and bores 209 infastener 201 is illustrative only, and it is to be understood that, inother embodiments, there could be as few as one head 103 and one bore209 or as many as three or more sets of heads 103 and bores 209. Also,it can readily be appreciated that head 103 could be replaced with anyof heads 23, 69 or 89.

Referring now to FIGS. 9( a) through 9(d), there are shown variousalternative embodiments of female portion 205 of fastener 201. In FIG.9( a), a female portion 301 is shown that is adapted for use with aone-headed male portion, female portion 301 additionally differing fromfemale portion 205 only in that it includes a generally disc-shaped base303.

In FIG. 9( b), there is shown another female portion 351 that is adaptedfor use with a one-headed male portion, female portion 351 additionallydiffering from female portion 205 only in that it includes three flanges353-1 through 353-3, instead of two flanges.

In FIG. 9( c), there is shown still another female portion 371 that isadapted for use with a one-headed male portion, female portion 371differing from female portion 351 only in that it includes five flanges373-1 through 373-5, instead of three flanges.

In FIG. 9( d), there is shown still yet another female portion 391 thatis adapted for use with a one-headed male portion, female portion 391differing from female portion 371 only in that it includes four flanges393-1 through 393-4, instead of five flanges.

It can readily be appreciated that the number of flanges in femaleportions 205, 301, 351, 371 and 391 are illustrative only and that othernumbers of flanges could be substituted. It can also readily beappreciated that female portions 351, 371 and 391 could be modified toinclude bases having a shape other than rectangular.

The biocompatible fastener of the present invention is not limited to atwo-piece, mating-type fastener and could also be, for example, a bonescrew, a surgical staple, or the like, wherein an intermediate portionalong the length thereof is made out of a bioabsorbable material havinga desired degradation rate and wherein the ends thereof are made out ofa non-bioabsorbable material or a bioabsorbable material having a slowerdegradation rate than the bioabsorbable material of the intermediateportion. In this manner, a biocompatible fastener can be designed thatfragments within the intermediate portion in a controllable andpredictable manner after a desired period of time.

The embodiments of the present invention recited herein are intended tobe merely exemplary and those skilled in the art will be able to makenumerous variations and modifications to it without departing from thespirit of the present invention. All such variations and modificationsare intended to be within the scope of the present invention as definedby the claims appended hereto.

1. A biocompatible fastener, said biocompatible fastener comprising apair of members matingly engageable with one another, at least one ofsaid members comprising an outer coating coated over an inner core, saidouter coating comprising a first bioabsorbable material, said inner corecomprising one of a second bioabsorbable material and anon-bioabsorbable material, said first bioabsorbable material having afirst degradation rate, said second bioabsorbable material having asecond degradation rate, said second degradation rate being slower thansaid first degradation rate, wherein, after said pair of members havebeen matingly engaged with one another, degradation of said outercoating over said inner core causes said pair of members to disengagefrom one another, and wherein one of said pair of members is a malemember and the other of said pair of members is a female member, saidmale member comprising a head, said female member comprising a boreadapted to receive said head and comprising a flange extending into saidbore, said head being engageable with said flange once said head hasbeen inserted therepast so as to inhibit withdrawal of said head.
 2. Thebiocompatible fastener as claimed in claim 1 wherein said inner corecomprises said non-bioabsorbable material.
 3. The biocompatible fasteneras claimed in claim 1 wherein said inner core comprises said secondbioabsorbable material.
 4. The biocompatible fastener as claimed inclaim 1 wherein only one of said members comprises said outer coatingcoated over said inner core.
 5. The biocompatible fastener as claimed inclaim 1 wherein said head comprises said outer coating coated over saidinner core and wherein degradation of said outer coating permitswithdrawal of said head past said flange.
 6. The biocompatible fasteneras claimed in claim 1 wherein said flange comprises said outer coatingcoated over said inner core and wherein degradation of said outercoating permits withdrawal of said head past said flange.
 7. Thebiocompatible fastener as claimed in claim 1 wherein said female membercomprises at least two flanges extending into said bore.
 8. Thebiocompatible fastener as claimed in claim 7 wherein said female membercomprises at least three flanges extending into said bore.
 9. Thebiocompatible fastener as claimed in claim 8 wherein said female membercomprises at least four flanges extending into said bore.
 10. Thebiocompatible fastener as claimed in 9 wherein said female membercomprises five flanges extending into said bore.
 11. The biocompatiblefastener as claimed in claim 1 wherein said female members comprises aflat base shaped to include said bore and said flange.
 12. Thebiocompatible fastener as claimed in claim 1 wherein said pair ofmembers are configured to fasten together two or more biologicalmaterials.
 13. A biocompatible fastener comprising: (a) a sleeve, saidsleeve defining a bore; (b) a substantially circumferential flangeformed on said sleeve and extending into said bore; (c) a male member,said male member comprising a post and a head disposed at first end ofsaid post, said head being insertable into said bore and past saidflange, said head being engageable with said flange once insertedtherepast so as to inhibit withdrawal of said head from said bore; (d)wherein at least one of said flange and said head comprises an outercoating material and an inner core material, said outer coating materialbeing a first bioabsorbable material having a first degradation rate,said inner core material being a material selected from the groupconsisting of a non-bioabsorbable material and a second bioabsorbablematerial, said second bioabsorbable material having a second degradationrate, said second degradation rate being slower than said firstdegradation rate; and (e) wherein degradation of said outer coatingmaterial facilitates withdrawal of said head past said flange.
 14. Thebiocompatible fastener as claimed in claim 13 further comprising a firstbase and a second base, said sleeve being mounted on said first base,said male member being mounted on said second base.
 15. Thebiocompatible fastener as claimed in claim 14 wherein said sleeve isprovided with a longitudinal slot.
 16. The biocompatible fastener asclaimed in claim 14 wherein said sleeve is provided with a pair oflongitudinal slots.
 17. The biocompatible fastener as claimed in claim14 wherein said sleeve terminates at one end in a sharp tip.
 18. Abiocompatible fastener comprising: (a) a male portion, said male portioncomprising (i) a first base member, said first base member having abottom surface, and (ii) a first male member mounted on said bottomsurface of said first base member, said first male member comprising apost extending downwardly from said bottom surface, said post having abottom end, and a head disposed at said bottom end of said post; and (b)a female portion, said female portion comprising (i) a second basemember, said second base member having a top surface, and (ii) a firstsleeve mounted on said top surface of said second base member andextending upwardly therefrom, said first sleeve defining a bore adaptedto receive said head and having at least one flange formed thereon, saidat least one flange extending into said bore, said at least one flangebeing engageable with said head once said head has been insertedtherepast so as to inhibit withdrawal of said head from said bore; (c)wherein at least one of said at least one flange and said head comprisesan outer coating coated over an inner core, said outer coatingcomprising a first bioabsorbable material, said inner core comprisingone of a non-bioabsorbable material and a second bioabsorbable material,said first bioabsorbable material having a first degradation rate, saidsecond bioabsorbable material having a second degradation rate, saidsecond degradation rate being slower than said first degradation rate;and (d) wherein degradation of said first bioabsorbable materialfacilitates withdrawal of said head past said at least one flange. 19.The biocompatible fastener as claimed in claim 18 wherein said head isgenerally conical in shape and terminate in a relatively sharp tip. 20.The biocompatible fastener as claimed in claim 18 wherein said firstmember is generally flat and oval.
 21. The biocompatible fastener asclaimed in claim 18 wherein said second base member is generally flatand oval.
 22. The biocompatible fastener as claimed in claim 18 whereinsaid first sleeve is provided with at least one longitudinal slot. 23.The biocompatible fastener as claimed in claim 18 wherein said firstsleeve is provided with a pair of longitudinal slots.
 24. Thebiocompatible fastener as claimed in claim 18 wherein said male portionfurther comprises a second male member mounted on said first base memberand extending downwardly therefrom, and said second male member beingidentical to said first male member, and wherein said female portionfurther comprising a second sleeve mounted on said second base memberand extending upwardly therefrom, said second sleeve being aligned withsaid second male member and being a mirror image of said first sleeve.25. A biocompatible fastener comprising: (a) a male portion, said maleportion comprising (i) a first base member, said first base memberhaving a bottom surface, and (ii) a first male member mounted on saidbottom surface of said first base member, said first male membercomprising a post extending downwardly from said bottom surface, saidpost having a bottom end, and a head disposed at said bottom end of saidpost; and (b) a female portion, said female portion comprising (i) asecond base member, said second base member having a top surface, and(ii) a first sleeve mounted on said top surface of said second basemember and extending upwardly therefrom, said first sleeve defining abore adapted to receive said head and having a flange formed thereon,said flange extending into said bore, said flange being engageable withsaid head once said head has been inserted therepast so as to inhibitwithdrawal of said head from said bore; (c) wherein at least one of saidflange and said head is at least partially made of a first bioabsorbablematerial having a first degradation rate and wherein at least one ofsaid first base member and said second base member comprises a materialselected from the group consisting of a non-bioabsorbable material and asecond bioabsorbable material, said second bioabsorbable material havinga second degradation rate, said second degradation rate being slowerthan said first degradation rate; (d) wherein degradation of said firstbioabsorbable material facilitates withdrawal of said head past saidflange and (e) wherein said first sleeve has a top end and wherein saidtop end is shaped to terminate in a relatively sharp tip.
 26. Thebiocompatible fastener as claimed in claim 1 wherein said head isgenerally conical.